Ozonolysis is a highly atom-efficient oxidative transformation, with two of the three oxygen atoms from the ozone molecule being incorporated into the products. Due to its ease of generation and its efficiency with regard to the oxidative cleavage of olefins, ozone has found use in a wide variety of applications, including chemical manufacturing and water disinfection.
When used in chemical manufacturing, ozonolysis requires a second step that destroys the peroxide and/or ozonide present in the reaction mixture before products are isolated. In the case of oxidative ozonolysis, the peroxides are further heated and oxidized in the presence of oxygen (O2) to generate products including carboxylic acid products. In the case of reductive ozonolysis, the peroxides and ozonides are quenched under reducing conditions, using hydrogen (H2) to give carbonyls and/or alcohols as the major products.
All ozonolysis processes require electricity and oxygen in order to generate ozone, and in the case of reductive ozonolysis, hydrogen may be used, as well. Historically, industrial oxygen production has been carried out mainly through the distillation or zeolite treatment of air, while H2 has been generated from the reformation of natural gas. See Cooke, S. J., Industrial Gases, Kent and Riegel's Handbook of Industrial Chemistry and Biotechnology, 11th ed., ch. 27, p. 1215 (2007); Hiller, H., Gas Production: Introduction, Ullmann's Encyclopedia of Industrial Chemistry, vol. 16, p. 403 (2012). More recently, however, electrolysis of water (H2O) using proton exchange membranes (PEM) has become a common method of oxygen and hydrogen generation as well. In the electrolysis of water, 2 moles of hydrogen are produced for every mole of oxygen making it highly amenable to generation of starting materials for reductive ozonolysis processes, as both gases are required for such processes.
Regardless of source, oxygen must be treated with electricity to generate ozone for the ozonolysis process. The ozone is then carried to the ozone reactor as a 0.1-20% mixture in a stream of oxygen. During the ozonolysis reaction, only the ozone is consumed and thus the oxygen must then be discarded, recycled, or used for an alternative purpose. Due to the cost associated with oxygen production, the preferred option has been to recycle the oxygen for continued ozone generation, using a corona discharge technique. See Vezzù, G., et al. IEEE Transactions on Plasma Science, Vol. 37, No. 6, p. 890-896 (2009).
While this process can be relatively efficient, there is a hazard associated with explosion due to organic contamination of the oxygen stream that is being recycled. Multiple condensers, precipitators, and/or filters are thus employed to manage this risk.
In addition to hazard reduction, the cost of electricity in the generation of ozone is a significant expense, and therefore a clean and efficient source of electricity would be desirable for the ozone generation process. Both fuel cells and hydrogen burning gas turbines offer such a solution. Fuel cells and gas turbines can use hydrogen and oxygen to generate electricity, with the reaction products being water and heat. While oxygen from ambient air can be used for these fuel cells, the fuel cells run at optimum efficiency in the presence of high purity oxygen and hydrogen. See Buchi, F. N., et al. On the Efficiency of Automotive H2/O2 PE Fuel Cell Systems, 3rd European PEFC, Session B09 (Thursday, 7 Jul. 2005). The deficiencies in current ozonolysis processes are addressed by the current invention. The invention disclosed herein arranges the ozonolysis process in such a way that the excess oxygen and hydrogen that are generated from the electrolysis step can be used to efficiently run a fuel cell or a gas turbine, thus significantly offsetting the net electricity required to generate ozone in a single-pass system.